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Packaging bag, and method for storing melt-processable polyvinyl alcohol resin with the use of the packaging bag

a technology of polyvinyl alcohol resin and packaging bag, which is applied in the field of packaging bags, can solve the problems of difficult stably melting-processing of pva resin, insufficient removal of organic solvent from pva resin, and inability to wash water-soluble pva resin, etc., and achieves the effect of cost and strength

Active Publication Date: 2018-12-06
MITSUBISHI CHEM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present patent provides a packaging bag for melt-processable PVA resin that is capable of releasing evaporated organic solvent during storage to improve forming stability of the resin. The inventors found that the packaging bag needs to have a specific physical property to allow the organic solvent to be released from the sealed resin. The packaging bag is made from a film with a specific methanol vapor transmission rate. By using this packaging bag, the organic solvent in the sealed resin is released in the form of vapor to dissipate, resulting in a reduced organic solvent concentration and improved forming stability of the melt-processable PVA resin. The film should also have a low water vapor transmission rate to prevent moisture absorption that could increase the volatile content of the resin. The packaging bag has a thickness of 10 to 2000 μm for cost and strength purposes.

Problems solved by technology

However, water-soluble PVA resin cannot be washed with water, so that the organic solvent (e.g., methanol) used in its production generally remains in the resin.
As a result, the organic solvent is not sufficiently removed from the PVA resin, but remains in the PVA resin.
If the melt-processable PVA resin containing the organic solvent is used as a material for melt processing, therefore, the organic solvent is evaporated from the PVA resin during the melt processing, making it difficult to stably melt-process the PVA resin.

Method used

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  • Packaging bag, and method for storing melt-processable polyvinyl alcohol resin with the use of the packaging bag
  • Packaging bag, and method for storing melt-processable polyvinyl alcohol resin with the use of the packaging bag

Examples

Experimental program
Comparison scheme
Effect test

example 1

[Side-Chain 1,2-Diol-Containing PVA Resin]

[0078]First, 76.6 parts (an initial feed ratio of 40%) of vinyl acetate, 14.2 parts of methanol and 9.2 parts (an initial feed ratio of 40%) of 3,4-diacetoxy-1-butene were fed into a reaction vessel provided with a reflux condenser and a stirrer, and then azobisisobutyronitrile was fed into the reaction vessel in an amount of 0.068 mol % based on the amount of the fed vinyl acetate. The resulting mixture was heated while being stirred in a nitrogen stream. Then, the rests of vinyl acetate and 3,4-diacetoxy-1-butene were fed dropwise at a constant rate for 13.5 hours, whereby polymerization was allowed to proceed. When the polymerization degree of vinyl acetate reached 91%, m-dinitrobenzene was added to the resulting mixture to terminate the polymerization. Subsequently, methanol vapor was blown into the resulting mixture, whereby unreacted vinyl acetate monomer was removed to the outside. Thus, a methanol solution of a copolymer was obtained...

example 2

[0088]A packaging bag was produced as having the same structure in substantially the same manner as in Example 1, except that the low-density polyethylene film for the methanol vapor permeable film layer had a thickness of 50 μm. The 50-μm thick low-density polyethylene film had a methanol vapor transmission rate of 7 g / m2·day (at 23° C. at 50% RH) and a water vapor transmission rate of 18 g / m2·day (at 40° C. at 90% RH). The pelletization of PVA resin stored in the packaging bag thus produced was evaluated in the same manner as in Example 1. The evaluation result is shown below in Table 1.

example 3

[0089]A packaging bag was produced as having the same structure in substantially the same manner as in Example 1, except that the low-density polyethylene film had a thickness of 30 μm. The 30-μm thick low-density polyethylene film had a methanol vapor transmission rate of 12 g / m2·day (at 23° C. at 50% RH) and a water vapor transmission rate of 30 g / m2·day (at 40° C. at 90% RH). The pelletization of PVA resin stored in the packaging bag thus produced was evaluated in the same manner as in Example 1. The evaluation result is shown below in Table 1.

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Abstract

A packaging bag for packaging a melt-processable polyvinyl alcohol resin is formed from a film having a methanol vapor transmission rate of 0.5 to 1000 g / m2·day. A method of storing a melt-processable polyvinyl alcohol resin includes the step of sealingly packaging melt-processable polyvinyl alcohol resin particles with the use of the packaging bag formed from the aforementioned film. Where the melt-processable polyvinyl alcohol resin is packaged with the use of the packaging bag, therefore, an organic solvent remaining in the packaged polyvinyl alcohol resin can be released in the form of vapor to the outside through the packaging bag to dissipate, whereby the resulting polyvinyl alcohol resin has a reduced organic solvent concentration after storage thereof in the packaging bag. As a result, the melt-processable polyvinyl alcohol resin is improved in forming stability.

Description

TECHNICAL FIELD[0001]The present disclosure relates to a packaging bag for packaging a melt-processable polyvinyl alcohol resin, and a method for storing the melt-processable polyvinyl alcohol resin with the use of the packaging bag. More specifically, the present disclosure relates to a packaging bag that ensures excellent forming stability of the melt-processable polyvinyl alcohol resin, and a method for storing the melt-processable polyvinyl alcohol resin.BACKGROUND ART[0002]A polyvinyl alcohol (hereinafter sometimes referred to as “PVA”) resin to be used for melt processing is typically synthesized with the use of an organic solvent such as methanol for production thereof. The PVA resin is generally stored and delivered in a solid form (in a powdery or granular form). In general, a melt-processable hydrophilic resin is packaged in a moisture resistant packaging bag (e.g., an aluminum bag) having an excellent water vapor barrier property for prevention of moisture absorption. Suc...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B65D65/40B65D81/26B32B27/10B32B27/32
CPCB65D65/40B65D81/26B32B27/10B32B27/32B32B2250/03B32B2250/40B32B2307/724B32B2307/732B32B2553/00B32B2439/46B32B27/08B32B27/285B32B27/34B32B27/36B32B27/40B32B29/002B32B2307/31B32B2307/7246
Inventor YAMAUCHI, YOSHIHITOSAKAI, NORIHITO
Owner MITSUBISHI CHEM CORP
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